U.S. Pat. No. 6,764,518 describes a prosthesis, for controlling the direction of flow in the gastro-intestinal tract of a living organism e.g. a mammal, consisting of a hollow elongate body consisting of a proximal elastic portion, that provides an annular fixing part, comprising a relatively thick wall having inner and outer surfaces that together define a cylindrical tube, comprising an elastic spring, such as a meandering nitinol spring or split ring, that extends substantially the length of the elastic portion, embedded within a biocompatible plastics material, and, joined integrally thereto, a distal flexible portion comprising a relatively thin wall having inner and outer surfaces that together define a tube having a passageway and consisting of a biocompatible plastics material. When exposed to a distorting pressure, the elastic portion can be folded e.g. to assist conveyance of the prosthesis with an endoscope, but is capable of returning to its normal undistorted shape once the distorting pressure is removed. In use, the elastic portion at the proximal end of the prosthesis is located e.g. in the esophagus or hiatus hernia, and the flexible portion at the distal end of the prosthesis extends down the tract into e.g. the stomach or intestine. When an overpressure is exerted on its outer surface, the flexible portion collapses on itself, so blocking the passageway and thereby preventing back-flow, as seen in GERD or gastroesophageal reflux disease. A prosthesis of similar design but being relatively longer and provided with relatively thicker walls than the above anti-reflux tubes can be used to reduce obesity by slowing down the ingestion of food in the gastro-intestinal tract, thereby inducing satiety, as described in US 2008-0249533 A1.
A prosthesis of the above design may be positioned in the gastro-intestinal tract by locating the elastic portion of the prosthesis in the natural “cavity” created by a fixed or sliding hiatus hernia, as illustrated in FIG. 1B (9) at least 1 cm high and no more than 6 cm high measured from the Z line (3), which is the junction of the esophageal mucosa and the gastric mucosa and the hiatus (5) or orifice of the diaphragm (4) that can easily and readily be seen and measured by any gastroenterologist practicing endoscopy. It is also possible to locate a prosthesis of the above design in the gastro-intestinal tract without having a hernia creating a distended area with the elastic portion positioned in the lower esophagus above the Z line (3), as illustrated in FIG. 1A. The diameter of the hernia or lower esophagus is measured with a calibration basket (12) that can be passed through the working channel of a standard gastroscope (10), as illustrated in FIG. 2. The calibration basket will enable the diameter of the hernia or esophagus to be measured, which in turn will determine the size of the prosthesis to be placed in the patient. When the elastic portion is correctly located, the flexible portion of the prosthesis extends from the elastic portion down the tract and into the stomach, where it may terminate at its distal end.
An endoscopic procedure may be employed to position a prosthesis in the gastro-intestinal tract. For example, a prosthesis having an elastic portion comprising a meandering nitinol spring, such as illustrated in FIG. 3 of U.S. Pat. No. 6,764,518 may be fitted by a procedure that typically comprises tightly folding the elastic portion and conveying the prosthesis with the endoscope, through the mouth and down the esophagus, where the prosthesis is released from the endoscope at or near to the position where the prosthesis is to be located. Releasing the elastic portion enables it to unfold and resume its normal undistorted shape in the gastro-intestinal tract. The prosthesis can be finally positioned, e.g. with the elastic portion located in the lower esophagus or hiatus hernia and the flexible portion extending down the tract into the stomach.
Once positioned in the gastro-intestinal tract, a prosthesis having an elastic portion comprising a meandering nitinol spring can be exposed to significant peristaltic movements that may push the prosthesis lower down the gastro-intestinal tract e.g. from the esophagus or hiatus hernia into the stomach or even further down into the intestinal tract.
To reduce the problem of the prosthesis becoming dislodged from its correct position within the gastro-intestinal tract, the meandering spring may be replaced by a split ring that extends substantially the length of the elastic portion, such as illustrated in FIG. 4 and FIG. 5 of U.S. Pat. No. 6,764,518. However, whilst such a prosthesis is less susceptible to being dislodged from its correct position by peristaltic forces, the continuous pressure exerted by the ring on the mucosal wall can cause local granulation (proliferation of tissue) that can occlude the prosthesis around the ring and/or cause bleeding ulcerations in the mucosal wall of the hernia.
The object of the present invention is to provide a prosthesis, consisting of hollow elongate body consisting of an elastic portion and a flexible portion, that is no more difficult to fit in position in the gastro-intestinal tract than the prostheses disclosed in U.S. Pat. No. 6,764,518 but which is less prone to displacement from its fitted position by peristaltic pressure than the prosthesis having an elastic portion comprising a meandering elastic spring and which is less prone to cause local granulation and/or ulceration that the prosthesis having an elastic portion comprising a slit ring.